An ESP32 ESPHome device in the furnace room reads a differential-pressure sensor across the filter and watches the furnace control board’s status LED. Home Assistant turns the raw pressure into blower speed, filter loading, and a replace-filter alert. The threshold comes from a real clean-filter-vs-old-filter experiment, not a guessed limit.

A basement dehumidifier whose built-in control restarts the compressor within 30 seconds of finishing a cycle. Two ESPHome boxes replace that with a wide, adjustable deadband and an anti-short-cycle timer, no Home Assistant, no cloud. Ships as three config pairs: a learning-only simple pair, a full pair for a home Wi-Fi network, and a full pair for buildings with no Wi-Fi at all.

Wiegand data lines idle at 5V, and the ESP32 is not 5V-tolerant. You don’t need a level-shifter IC or a resistor divider. A single signal diode does the job, and it does it better.

MicroPython rewrite of the Impression 5 giant calculator. 9-digit NeoPixel 7-segment display with 20 physical buttons, running on ESP32 or Raspberry Pi Pico.

ESPHome config for a Wiegand keypad reader built on a thin-edge philosophy: the device only captures input and relays it to Home Assistant. Now folded directly into the garage’s RATGDO board instead of running on its own standalone ESP32.